Automatic tuning mechanism



.June 10, 1941 F. L. CREAGER AUTOMATIC TUNING MECHANISM Filed Sept. 24,1937 4 Sheets-Sheet l 5 7"" l We I L u# l I e J6 j 'd i7 57 4Z 24 53674Z 6 Z June l0, 1941. F L, CREAGER 2,244,678

AUTOMATIC TUNING` MECHANISM Filed Sept. 24, 1957 4 Sheets-Sheet 2Smaentor ,ede/M bagger June 10, 1941- F. L. cREAGl-:R

AUTOMTIC TUNING MECHANISM Filed Sept. 24. 1937 4 Sheets-Sheet 3:inventor Gttorneg June 1o, 1941.

F. L. CREAGER AUTOMATIC TUNING MEcHANIsM Filed sept.' 24, 1937 4SheetSI-Sheet 4 Zhwentor Cttorneg Patented June 10, 1941 AUTOMATICTUNING MECHANISM Frederick L. Creager, Camden, N. J., assignor to RadioCorporation of America, a corporation of Delaware Application September24, 1937, Serial No. 165,469

This invention relates to automatic tuning control systems for radioapparatus and the like, and particularly to a system wherein the tuningelement of the controlled apparatus is actuated by mechanical means, asdistinguished from systems employing electric motors for the samepurpose.

' A principal object of the present invention is to provide an improvedand simplified automatic tuner of the mechanical preselection type.

Another object of' the invention is to provide an extremely simple,inexpensive, compact, accurate and trouble-free selector mechanism forradio receivers, and one which lends itself readily to mass productionmethods.

Another object of the invention is to provide an automatic stationselectorof the :type above referred to and wherein the stations may heVset up conveniently from the exterior of the cabinet which houses theset.

Another object of the invention is to provide an automatic stationselector capable of tuningin a desired maximum of stations, and this toowith 'the application of a minimum intensity oi actuating force.

A further object of the invention is to provide a tuning deviceemploying push-buttons for selecting the more frequently tuned-stations(for example, local stations) and provided with the usual rotary knopfor tuning the less `frequently dialed stations (for example, distantand short- Wave stations) and wherein the push-buttons areself-disengaging whereoy the tuning mechanism is automatically clearedso that changeover from one inode of operation to: the other isaccomplished at will` and Without in wise affecting the set-up ofthepreselector mechanism.

Still another object of the invention is to provide a novel Amechanismfor converting a simple thrust movement, applied selectively to any ofseveral push-buttons, into torque capable of driving a, rotor shaftthrough its entire range oi movement, said mechanism being characterizedby an economy and simplicity of parts.

Certain details of construction together with additional objects andadvantages will be apparent and the invention itself will be ,morereadily understood by reference to the following specification and tothe accompanying drawings, wherein Figure l is a tcp plan view of aportion ci a radio receiver provided with an automatic tun'- ing controlmechanism embodying'the invention,

Figure 2 is a front Vview in elevation of the apparatus yof Fig. 1, I Y

Figure 3 is a sectional View of the actuating mechanism taken on theline 3-3 of Fig. 2.,

Figures 4 and 5 are elevational views, partly in section of alternativeforms of driving elements suitable for use with the selector mechanism oi the invention,

Figure 6 is a front View in elevation of another form of rack or drivenmember and showing an alternative arrangement of the station-selectingbuttons or driving members, Y

Figure '7 is a front view in elevation of another embodiment oftheinvention,

Figure 8 is a sectional view taken on the Vline 8 8 ofFig. 7, and

Figure 9 is a sectional view taken on the line U9 9 of Fig. 7 and showscertain details of the actuating element there employed.

Referring noW to Figs. l, 2 Yand 3, wherein like reference charactersdesignate the saine parts in each gure: Here l designates generally aportion of a radio receiver chassis having a front panel 2 and a shelf`or'base 3 upon which base certain component parts such, for example, astubes 4, a coil 5, a transformer 6, a fixed capacitor 1, and a. variabletuning element 8, are mounted. The tuning element 8 may ,be constitutedoy a frame 9 containing one or more units l0 and i! including theusualstator AI2 and rotor plates I3. The rotor plates are mounted on acommon tum ing shaft I4 which is adapted itc he rotated through a rangeof in a manner later described.

As shown more clearly in Figs. 1 and 3, a mounting plate I5 Ais securedto the front panel 2 of the chassis l, as by hollow studs i6, Ita, and

'is braced by additional studs or spacers Il iixed to the 4condenser.frame 9. The mounting plate i5 in .turn supports a front dial plate I8which is Ispaced therefrom and secured thereto by spacers I9 (Fig. 3).

An extension Ma of the main tuning shaft. I4 extends through plates l5and I8 and is provided with .a double ended pointer 20 which is iixe'ddirectly on the end of the extension la so that its position accuratelydepicts the angular position of the main tuning shaft i4, and hence thesetting of the condenser 8. The pointer 20,`When read in connection witha dial 2l on the front plate 18,'thus indicates the exact frequency toWhich the receiver Sis tuned.

The radio receiverv which has been selected for purposes of illustrationwill be understood to comprise a two-band set having la band selectorswitch indicated generally at '22 (Fig. l) and a .dial -2l which isprovided with a pali' of 180 arcuate scales 2id and 2|b. One of thescales, say the top scale 2id, is allotted to the broadcast zband, andthe bottom scale, 2lb, to another band, say a short-wave band. Thecorrespondingly lettered ends of the double-ended pointer 26 areindividual to these 180D dial scales. The band switch 22 may, as sho-wnin Fig. 1, be controlled by a knob 2 3 `affixed to a shaft 24 whichextends to the front of the set through one of the hollow spacers i3which :supports the mounting plate I5.

As shown more clearly in Fig. 3, a seco-nd knob 25 on the end of atuning control shaft 23, which extends from the front panel 2 of thechassis, through supporting stud Ilia and the mounting plate l5,provides means for making tuning adjustments when the band selector 22(Figs. l and 2) is switched to that position whereat the receiver iscapable of translating short-waves. Knob 25 may also be employedindependently of the selector mechanism, later described for loggingstations in the broadcast band.

The shaft 26 to which the tuning knob 25 is attached carries a pinion 2l(see Figs. 3 and 2) the teeth of which mesh with complementary teeth 28on a dependent section 29 of a rack 33. This drive element 33 issupported for linear movement as in a groove |5a in-the mounting plateI5. The upper edge of rack 33 is provided intermediate its ends with atoothed segment 3| which serves to drive a gear wheel 32 which ismounted for rota'tion as on a stud shaft 32a carried by the mountingplate i5. Gear 32, in turn, drives a pinion 33 carried on the maintuning shaft I4, so that this shaft and the rotor described, is of moreor less conventional design.

The automatic station selector of the invention utilizes the rack 3|),gears 3|, 32 and 33, and additional elements including a plurality ofpre-set adjustable male members or stops 33d, 34h,

34o, 34d and 33e, o-ne for each pre-selected station, and female orstop-engaging members 35a, 35h, 35e, 35d and 35e, individual,respectively, to each stop 34. The stop engaging members 35 are thedriving elements of the preselector; each is affixed to the end of ahollow plunger 35, and the plungers are journaled in and are supportedby the plate i8 which supports the tuning dial 2|. The plungers arepreferably equally spaced and each is provided with a spring 31 forreturning it to its idle position. If desired, these springs may becovered by caps, not shown. The pre-set s'tops 34 are the drivenmembers; they are adjustably secured to the rack 3i), each by a screw 38(Fig. 3) which extends rearwardly through one of a number of slots 39with which the rack is provided. These screws 38 terminate within thegroove |5a of the mounting plate I5; a nut 4Q, on each screw, retainseach stop 34 against displacement with respect to the rack 33. The nutsare prevented from turning by contact with the to-p and bottom surfacesof *the groove, whereby the, screws are readily turned therein.

As clearly shown in Fig. 3, each stop or male member 34 may be in theform of a 90 includedangle icone and each stop-engaging or female member35 has an opening of complementary contour for receiving and vcenteringits stop when the plunger 36, to which the stop is affixed, is thrustinwardly. Each stop is provided This condition is fulfilled when (a) thelarge at its apex with a slot 4I so that it may be loosened andtightened as by means cf a screw driver (not shown). Adjustment of eachstop may be made from the front of the set by removing a spring-retainedcap 42 on the end of the plungers 36 and inserting the tool through thebore.

As previously indicated, the main tuning shaft I4 has a, 180 range ofrotation. Thus, to rctate this shaft through its entire range of move--ment the length of the toothed segment 3| on rack 30 should be no lessthan one-half the circumference of the pinion 33, for it is thatdistance which the rack must travel to rotate the tuning elemen't fromone limit of its movement to the other. Now, since one of thepreselected stations to which the set is to be automatically tuned maybe at one end of the scale (2H) and another at the other end, it isobvious that each stop engaging member 35 must be capable of driving itsstop 34 (and hence the rack 3i) and condenser shaft I4) this maximumdistance.

diameter of the opening 35' in the stop-engaging members 35 issubstantially twice 'the length the rack must travel in driving thecondenser shaft through its entire 180 range of movement and (b) wheneach stop 34 is so positioned with respect to its stop-engaging member35 that its apex at all times falls within the large circumference ofthe opening 35' of the stop-engaging member to which it is presented. Inthis latter connection (b) i't. Will be noted that the length of eachslot 39 in which the individual stops 34 are secured is such as toensure that the apex of each stop will fall within the boundaries of itsstop-engaging member 35.

The automatic tuner of the receiving set shown in Figs. l and 2 isprovided with iive plungers or push-buttons 36 and a similar number ofstops 34 and stop-engaging members 35 It is thus capable of rotating themain tuning shaft I4 selectively and automatically to any ve angularpositions required to achieve that number of different stationfrequencies.

Assuming now that it is desired to set-up the automatic tuning mechanismof Figs. 1 and 2. In order to do this the cap 42 on each plunger 36 isremoved and each stop 34 loosened as by means of a screw driver (notshown) which is inserted through the bore of the plunger into engagementwith the slot 4l with which each stop is provided (see Fig. 3). With thecurrent turned on, the manual tuning knob 25 is then rotated to bring inthe rst of the desired stations. With the set perfectly tuned to thatfrequency, one (any one) of the plungers 36 is pressed in to the limitof its movement. Since the stops 34 have been loosened, each is free tomove with respect to the rack 3i). This relative movement is initiatedwhen the stop 3d contacts the wall of the opening 35' in the inwardlymoving stop-engaging member 35, and terminates when that stop isperfectly centered with respect to its stop-engaging member. Thecorrectly centered stop is then tightened on the rack, some care beingtaken that the rack is not inadvertently moved during the tighteningoperation. Thus, the apparatus is set up for one station.

The manual tuning knob 25 is then turned to tune the apparatus to thefrequency of a second desired station. Another button or plunger isassigned to this station and the stop individual to the selected plungeris centered with respect toits stop-engaging member (lby pressing inthatplunger) and then vtightened on the rack by means of the screw driver.The other stations are set up in the same manner.v `It is immaterialwhich plunger is assigned to a given station frequency. For example, itis not necessary that a. button on the left f center be assigned to astation whose frequency is indicated at a point on the left side of thedial.

Referring particularly to Fig. l: When the apparatus is set up to thedifferent stations, the stops (ve in this case) 34a, 34h, etc. arespaced different distances from each other (and .hence differentdistances from the respective centers of' the uniformlyspacedstop-engaging members 35, 35h, etc.), as determined by thedifferent degrees of rotation required by the rack 30 to rotate thecondenser shaft I4 from any given angular position to any of theselected positions whereat a particular station is tuned in.

' As previously set forth, regardless of the relative setting of thestops, the apex of each stop is always directed to a point within theopening of its stop-engaging member. It will, therefore, be apparentthat each stop engaging member is adapted to engage and to drive itsstop irrespective of the position of the rack upon which the stops aremounted. Thus, regardless of the frequency `to which the receiver haspreviously been tuned, the actuation of a plunger (say 36d, Fig. 1)individual to another station will bring the inclined surface of thestop-engaging member 35d on the end of that plunger 36d, into contactwith a portion of the surface of its stop 34d and continued inwardmovement of the plunger will cause a movement of the stop 34d (and henceof the rack 30, gears 32, 33, and tuning shaft I4) which movement is nothalted until the stop is perfectly centered in its stop-engaging member,at which 4time the plunger will have reached the limit of its movement.Each pair of complementary members 34--35 may therefore be said toinclude means operable at the limit of the above-described movement forlocating the variable tuning element at the position whereat theselected frequency, individual to each stop and its stop-engagingmember, is achieved.

As previously set forth, each button or plunger 3B is preferablyprovided with a spring 31 for returning ilt to its idle position. Intheir idle positions, the stop-engaging members 35 are out of engagementwith their stops 34 so that the set is in condition to be operatedeither automatically by means of the plungers 35 or manually by means ofthe tuning knob 25. changeover from one mode of operation is thuspossible without any positive supplementary action on the part oftheoperator.

The stops 34 need not necessarily be in the form of 90 included anglecones, as shown in Figs. 1, 2 and 3, but may be mere cylinders, asindicated at 44, Fig. 4, in which case the end presented to thestop-engaging member 45 is preferably rounded, as shown at 44a.Alternatively, and as shown in Fig. 5, the stops'may beV in the form ofa generally conical member 54 having two surfaces of revolution (54a and54h) `exhibiting different degrees Vof convergence, in Which case theangle of that portion 51|a of its surface adjacent its base preferablyis the same as thatof its stop-engaging member 55. The stops 44 and 54of Figs. 4 and 5 respectively possess the advantage of requiring lessforce to initiate their movement. This is so because only a smallfraction of their surfaces of revolution is in contact with thestopeeng'aging rmembers at the time when they are beingmoved. Further,the angle of engagement is smaller and the subsequent movement is morein the nature of a thrusting than wedging movement.

VThe driven member or rack, 30, of the embodiment of 'the inventionshown in Figs. 1, 2 and 3 is a inere strip of metal with the stops 34arranged in line thereon, and the actuating mem-V bers 36 are similarlyarranged, in register with these stops, beneath the dial 2 I. Otherarrangements of the station selecting or actuating members may be madeWithout departing fromthe spirit or scope of the invention. Thus, inFig. 6 a four sided rack, here designated |30, is shown, making itpractical to distribute the stops |34 and hence the selector buttons orplungers |36 at various points about the dial plate I I8. In thisembodiment of the invention, the slots |39, in which the stops |34 Yareadjustably fixed, are arranged in two groups of three, the slots in eachgroup (one group is on the left arm of the rack |30V and the other groupon the right arm) are arranged one above and in line with another. As

- in the first described embodiment of the invention, the long dimensionof these duplicate slots, and hence the limits within which each stopmust be set, corresponds to the distance the rack must be moved torotate the tuning shaft II4 through its entire range of movement. Aspreviously described, the stops are individual to the separatefrequencies and are relatively spaced in their slots as determined bythe different degrees of movement required by the rack to rotate thetuning shaft from any given position to any of the selected positionsindividual to the different station frequencies. The plunger |36 towhich the sto-p-engaging members |35 are affixed are prei'- erablyequally spaced from each other on the dial plate IIB.

Referring still to Fig. 6, the tuning control knob |25 is here showndisposed in line with the center of the dial plate. The pinion |2'I andteeth |28 actuated by the shaft |36 to which knob |35 isafiixed areconveniently similarly disposed. The knob |23 for actuating the wavechange switch and another knob |23a for actuating a manual volumecontrol (not shown) are shown arranged, in the interests of symmetry, onopposite sides of the tuning control knob |35. The embodiment of theinvention shown in Fig. 6 may otherwise be similar in all respects tothat shown in Figs. 1 and 5, inclusive.

In the embodiments of the invention thus far described. the drivingelements or stop-engaging members 35, Figs. 1 to 3; 45, Fig. 4; 55, Fig.5; and |35, Fig. 6, are female elements and the stops 34, Figs. 1 to 3;44, Fig. 4; 54, Fig. 5; and |34, Fig. 6, are male elements. The relativeform of the stops and stop-engaging members may be reversed if desired.This is brought out, together with certain other modifications, in theembodiment of the invention shown in Figs. '7 to 9, inclusive.

In Figs. 'I to 9, the main tuning shaft is designated 2I4, the rearmounting plate 2|5, and

the dial plate 2|8. As in the previously described embodiments atwo-band dial scale 22| and double-ended pointer 22|) are shown. In

the interests of simplicity these drawings show but two stationselecting elements 242. They are 'arranged on one side of the dialplate. Each element or button 242 has an extension 242a (Fig. 9) of areduced diameter which is journaled for Iaxial movement in the rearmounting plate 2|5 and is provided intermediate its ends with a male(instead of a female) driving or stop-engaging element 235 of conicalcontour.- When a button is depressed, the sloping surface of the maleelement thereon will engage a complementary sloping surface of a drivenfemale` or stop element 234 which may constitute an orifice having abevelled rim 234a arranged adjacent the end portion of a surface of anarm 230 which is pivoted as at 2322L on the rear mounting plate 2 I5.Only one female element may be arranged on any given arm since each isindividual to a given station frequency. When a given arm is actuated(by the force incident to the centering of its male and female elements)its movement Will be a pivotal one, about the common axis 232a of theseveral arms 23H. instead of a linear movement, as in the case of thedriven element (rack 30, or 130) of the earlier described embodiments ofthe invention.

The pivotal movement of an arm 235!V serves vto move a gear sector 232to which the several arms are fixed as by means of a washer 232b (see`Fig. 8). lThe gear sector in turn drives a pinion 233 secured'to themain tuning shaft 2M. The degree of movement imparted to the gears2152-233 and shaft 2id depends upon the arcuate distance an arm 23! mustbe moved to center its stop-engaging male element 235 with` respect toits stop or female element 234. The curved arrows adjacent the ends ofthe .arms indicate such pivotal or arcuate movement.

:In order to` rotate the shaft 2M to the different `angular settingsrequired to achieve the selected station frequencies, the arms 23|] mustbe xed to the gear sector at certain angles. (It will be noted inconnection with Fig. 7 that the arms 23B intersect the line -B atdifferent Y angles.) To adjust the relative angle between arms 23H3,first one and then another of the buttons 2132 is depressed and held inWhile the tuning knob 225 is forcibly turned, (to overcome the frictionof the washer 2321)) to the desired stations. Torque applied to knob 225and Vtransmitted through gear 221 and pinion 233 to the gear sector 232will serve to move the gear sector with respect to that arm which isbeing momentarily held against movement. Thereafter (the buttons beingreleased), each arm 23) s relatively fixed with respect to the gearsector 232 by the friction Washer 232b and movement of an arm resultingfrom, the centering action of the male and female elements 235, 234,produces a corresponding movement of the gear sector 232 and tuningshaft 2M.

Obviously, more than two arms can be affixed to the gear sectorproviding only that they are preset at different angles. Alternatively,a second, or indeed a third, sector (not shown) all meshing, if desired,with the same pinion 233 lmay be provided. Other modifications willsuggest themselves to those skilled in the art. It is to be understood,therefore, that the foregoing is to be interpreted as illustrative andnot in a limiting sense, except as required by the Y prior art and thespirit of the appended claims.

What is claimed is:

1. In a radio apparatus, an element to be tuned, a rotor shaft on Whichsaid element is mounted, driven means connected to said shaft, a`plurality of preset adjustable stops on said driven means and throughwhich a driving force for rotatingvsaid shaft may be applied to saiddriven means,` and a movable sto-"p engaging member for applying saiddriving force mounted adjacent each stop, said stops and stop engagingmembers comprising male and female ele-` ments, the opening in eachfemale element bee ing of a diameter sufficient to permit the entrancetherein of its male element irrespective of the position to which saiddriven means may be moved.

2. The invention as set forth in claim 1 wherein said driven means isconstituted by a toothed rack having duplicate slots therein Withinwhich said pre-set stops are seated, and wherein the dimensions of eachof said slots and hence the limits within which each stop must be setcorrespondsl to the distance said rack must be moved to rotate saidshaft through its entire range of movement.

3. The invention las set forth in cla-im 1 wherein said stop engagingmembers are contained on plungers mounted for axial movement and whichextendzto the exterior of said apparatus, said plungers being hollow topermit of access to said pre-set stops for purposes of adjustment.

4. In a radio apparatus, a variable tuning element requiring differentdegrees of angular movement to tune said apparatus to separate selectedfrequencies, a rotor shaft on which said tuning element is mounted, adriven element connected to said shaft for rotating said shaft throughits entire range of movement, and means for selectively applying adriving force to said rotor shaft through said driven element suhicientto move said variable tuning element from any given position to any ofsaid selected angular positions, said driving means comprising aplurality of spaced stops mounted on said driven element, a plurality ofmovable female stop-engagingmembers individual to said stops and each ofa diametersuflicient to engage its stop irrespective of the position ofsaid driven element, and means including the selected stop and itsstop-engaging member for halting the y. movement of said driven elementwhen said rotor shaft completes Vthe movement it requires to move saidtuning element to that angular position whereat the selected frequencyis achieved.

5. In a radio apparatus, a variable tuning element, a rotor shaft onwhich said element is mounted, driving and driven elements operativelyconnected to said shaft for rotating said shaft through its entire rangeof movement, and auxiliary means for rotating said shaft from any givenangular position to any of a plurality of selected angular positions,said auxiliary means comprising a plurality of pre-set adjustable stopsof substantially conical contour mounted on a common driven element forapplying a driving force thereto, said stops being spaced one fromanother as determined Yby the different degrees of movement requiredbysaid driven means to rotate said shaft from the limits of its movementto any given of said selected angular positions, a movable stop engagingmember for each stop for applying a driving force to said drivenelement, said stop engaging members each beingk of a contourcomplementary to its stop and of a diameter sufficient to engage and todrive its stop irrespective of the position of said driven element.

FREDERICK L. CREAGER.

